doc: Use markdown syntax for xrefs

Syntax is taken from MyST:

https://myst-parser.readthedocs.io/en/latest/using/syntax.html#targets-and-cross-referencing

1 files changed, 24 insertions, 0 deletions

diff --git a/doc/labelless-link-is-xref.lua b/doc/labelless-link-is-xref.lua
new file mode 100644
index 00000000000..67569b02091
--- /dev/null
+++ b/doc/labelless-link-is-xref.lua
@@ -0,0 +1,24 @@
+local function starts_with(start, str)
+  return str:sub(1, #start) == start
+end
+
+local function escape_xml_arg(arg)
+  amps = arg:gsub('&', '&')
+  amps_quotes = amps:gsub('"', '"')
+  amps_quotes_lt = amps_quotes:gsub('<', '&lt;')
+
+  return amps_quotes_lt
+end
+
+function Link(elem)
+  has_no_content = #elem.content == 0
+  targets_anchor = starts_with('#', elem.target)
+  has_no_attributes = elem.title == '' and elem.identifier == '' and #elem.classes == 0 and #elem.attributes == 0
+
+  if has_no_content and targets_anchor and has_no_attributes then
+    -- xref expects idref without the pound-sign
+    target_without_hash = elem.target:sub(2, #elem.target)
+
+    return pandoc.RawInline('docbook', '<xref linkend="' .. escape_xml_arg(target_without_hash) .. '" />')
+  end
+end